I made this for a friend. It fits an 28mm wide optic. The scale might have to be adjusted +/- 1% for a perfekt fit, because some of the optics have a slight cone shape.

For best result print in clear PETG or PLA. It makes the lines almost invisible when focusing on the background If the killflash gets to big you can add some tape around the rim to ensure a tight fit and prevent scratches on the optic